Big edit for this post, you posted the Kerdi shot while I was typing. So... 1) The flex in the floor that is causing the grout to crack: It's possible that the Kerdi Tray was not properly bedded in thinset, so as the slightly flexible tray flexes, the inflexible grout is cracking. It's also possible that the small size of the penny rounds is resulting in point loading on the foam tray. The foam compresses ever-so-slightly, the tile moves, the grout cracks. The floor...Is your guy using thinset as grout? Grout as thinset? With the penny rounds, it almost looks like he's doing an all-at-once installation. Setting the tile, promoting between-the-tile-squeeze-through, then grouting. All at the same time. A negative with that is that he's grouting and cleaning the grout before the thinset has fully cured. When I grout I'm pretty aggressive with the grout float in order to get grout into every nook and cranny. I don't want to leave any voids. If your guy took it easy when grouting so as to not displace the unbonded sheets of penny rounds, he could have left a few voids beneath the surface. If he wanted to be gentle while cleaning the grout, he might have used too much water during cleanup, that can also weaken the grout. I don't know why the floor is being grouted piecemeal. That's an easy way to get uneven grout color on a floor. As he continues to tile, he'll have to chip out parts of the hardened thinset/grout at the edges fo the already installed sheets to get the subsequent sheets of tile to mesh with the already installed sheets. He'll need to be careful to not ding the Kerdi membrane. It's also a recipe for mismatched spacing at the edges resulting in being able to see the individual sheets of tile versus the floor being one harmonious surface of penny rounds. With him sliding the floor tile under the bottom course of wall tile, I do hope he's not leaving any unfilled voids in the floor-wall corners. 2) Bullnosing. He bullnosed the tile after they were on the wall? Yeah. Probably not going to get a good outcome. Should be an easy remove and replace. The bowed wall? The tiler tiles on what he gets. If he gets a bowed wall courtesy of the framers, he can put the blinders on and tile right over it...or he can address the bowed walls with whoever hired him...the GC? The homeowner? Then the tiler can either tile right over the bowed wall, OR he can have the contractor fix the wall before he tiles, OR he can repair the wall himself and then tile. One added item...I can't tell what exactly is going on int he bottom left corner of the already installed tile. Could simply be that the tile spacing is skewed and he lost the pattern. After this floor is done and everything cured, I'd recommend having the GC pull the drain grate, install a plug, and flood the floor. As the floor tile is covered with water, watch for air bubbles. They'll indicate voids under the tile or in the corners. Once flooded, pull the plug to see how the floor drains. Make sure it drains completely and that water is not held in the corners. With a Kerdi Tray, the slope of the floor and a properly draining floor should be a no-brainer. But based on what I'm seeing and what you described regarding the bullnose, this could be a "no brain" installation. Sorry for that. Remediation after-the-fact is always a tough spot to be in. Good luck.

I completely agree with Nancy. There are too many bad boards. They should not have put them down with with those bad ends. Filler is commonly used in hardwood flooring. There's nothing wrong with using filler. But, I don't think it's a good solution for those widespread (and shallow) corner chips. Filler is better used to fill in small gaps here and there in a floor. By the way, filler shows. It is not invisible. It looks fine when you have filler here and there, but not when it's everywhere. It IS completely irrelevant to the current situation whether or not you will have good humidity control in that room in the future and what anyone's opinion is about whether or not you will have problems with the floor in the future because of that. You don't deserve a bad floor now because someone thinks you'll have problems in the future or because they think you shouldn't have used wood in the first place. You are paying for good floor install and finish now and that's what you should get.

" I would attack’s it with a sponge at least to see if you can clean that up." You do that and you own the entire thing, make him clean it up better. Sooner the better as grout hardens over time. Also as alluded to above he needs to remove the grout at all chnages of plane and use 100% silicone caulk.

Uh oh...,"...that's something I'll negotiate during the final billing." Sorry but that won't work. If they feel you 'won't pay' then they will walk off the job. If a company is so low on skill that it can't handle a ROUTINE subfloor levelling (this should be part of their daily bread...hmmmm) then they will be low enough on the honour scale to walk without a backwards glance. I guarantee it. You better get this sorted out BEFORE anything is touched. As soon as you touch this mess BEFORE things have been ironed out, you OWN the issues. I mean it. I'm trying to gently put my foot down FOR you...but it will still hurt you to hear what I'm saying. In building 'law' (depends on what state you are in) the 'last guy' who touches something 'OWNS IT'. Not kidding. If you allow SOMEONE ELSE to do anything to this floor without PRIOR WRITTEN AGREEMENT with the original company, you will be left hold this bag of whack-job-flooring install. Hash this out. Get it in writing and ORDER IN enough flooring to refinish the entire floor. 'Cause I can guarantee you will lose more than 50sf of wood. I expect a full 75% loss of wood. The glue on the edges will NOT let go. It will CRACK the planks to remove them. The glue is the TOUGHEST surface. The wood is the weakest. The weakest surface will brake...not the toughest. Please do NOT start this until EVERY KINK is ironed out and in writing with dates, signatures and WITNESS signature! I'm not kidding. If these guys can't figure out how to level an ENTIRE condo...then they won't be able to figure out how to 'save' a glue-edge floating wood floor. Assume nothing. Write down EVERYTHING. Preferably in emails...or write the email to the store reiterating what you spoke about over the phone. She who owns the most evidence wins.